The Wilsons use good drivers in exceptional cabinets, and it is the cabinets that are hardest to reproduce, especially using MDF.
I'd malso suggest a WATT/Puppy clone and there are several designs listed above. You could do a search for Wilson clones using Google. I've seen WAMM clones I think but I don't recall where.
If I were building a WATT/Puppy clone, I would try to match the original as there are newer, poissibly better drivers and the crossover would be too tough.
I'd look at something like SEAS W26 for the Puppies instead of Dynaudio 21w54 they used. Then the SEAS W18 EX for the midrange instead of the Scanspeak 8545 and either the SEAS Millenium tweeter or the Focal Audiom mentioned above.
As far as cabinets, build them using the thickest MDF you can with good bracing, and I'd seriously consider having the front baffle made out of Corian.
I'm not a crossover expert but if it were me I'd use an active digital crossover like the dbx Driverack PA (www.driverack.com) and triamping.
This way you can measure and tweak to your hearts content.
You could build the above for $1600 for the drivers, $500 for the crossover and the cost of the cabinets. It should sound great done well.
Good luck